Face Your Fears: Cleaning Gobies Inspect Predators despite Being Stressed by Them

Social stressors typically elicit two distinct behavioural responses in vertebrates: an active response (i.e., “fight or flight”) or behavioural inhibition (i.e., freezing). Here, we report an interesting exception to this dichotomy in a Caribbean cleaner fish, which interacts with a wide variety of reef fish clients, including predatory species. Cleaning gobies appraise predatory clients as potential threat and become stressed in their presence, as evidenced by their higher cortisol levels when exposed to predatory rather than to non-predatory clients. Nevertheless, cleaning gobies neither flee nor freeze in response to dangerous clients but instead approach predators faster (both in captivity and in the wild), and interact longer with these clients than with non-predatory clients (in the wild). We hypothesise that cleaners interrupt the potentially harmful physiological consequences elicited by predatory clients by becoming increasingly proactive and by reducing the time elapsed between client approach and the start of the interaction process. The activation of a stress response may therefore also be responsible for the longer cleaning service provided by these cleaners to predatory clients in the wild. Future experimental studies may reveal similar patterns in other social vertebrate species when, for instance, individuals approach an opponent for reconciliation after a conflict

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Cleaning in pairs enhances honesty in male cleaning gobies

A recent game theoretic model akin to an iterated prisoner's dilemma explored situations in which 2 individuals (the service providers) interact simultaneously with the same service recipient (the client). If providing a dishonest service pays, then each service provider may be tempted to cheat before its partner, even if cheating causes the client's departure; however, a theoretical cooperative solution also exists where both partners should reduce cheating rates. This prediction is supported by indirect measures of cheating (i.e., inferred from client responses) by pairs of Indo-Pacific bluestreak cleaner wrasses Labroides dimidiatus. Here, we examine how inspecting in pairs affects service quality in Caribbean cleaning gobies Elacatinus spp. We measured dishonesty directly by examining the stomach contents of solitary and paired individuals and calculating the ratio of scales to ectoparasites ingested. We found that the propensity to cheat of females and males differed: females always cleaned relatively honestly, whereas males cheated less when cleaning in pairs than when cleaning alone. However, overall, the cleaning service of single and paired individuals was similar. Our results confirm that cleaners cooperate when cleaning in pairs; however, our findings differ from the specific predictions of the model and the observations on L. dimidiatus. The differences may be due to differences in mating systems and cleaner-client interactions between the 2 cleaner fish specie

Dopamine modulates social behaviour in cooperatively breeding fish.

Dopamine is part of the reward system triggering the social decision-making network in the brain. It has hence great potential importance in the regulation of social behaviour, but its significance in the control of behaviour in highly social animals is currently limited. We studied the role of the dopaminergic system in social decision-making in the cooperatively breeding cichlid fish, Neolamprologus pulcher, by blocking or stimulating the dopaminergic D1-like and D2-like receptors. We first tested the effects of different dosages and timing of administration on subordinate group members' social behaviour within the group in an unchallenging environment. In a second experiment we pharmacologically manipulated D1-like and D2-like receptors while experimentally challenging N. pulcher groups by presenting an egg predator, and by increasing the need for territory maintenance through digging out sand from the shelter. Our results show that the D1-like and D2-like receptor pathways are differently involved in the modulation of aggressive, submissive and affiliative behaviours. Interestingly, the environmental context seems particularly crucial regarding the role of the D2-like receptors in behavioural regulation of social encounters among group members, indicating a potential pathway in agonistic and cooperative interactions in a pay-to-stay scenario. We discuss the importance of environmental information in mediating the role of dopamine for the modulation of social behaviour

Short-term exposure to elevated CO2 stimulates growth and metabolic responses that alleviate early-stage iron deficiency symptoms in soybean

Elevated CO2 (eCO(2)) increase plant biomass and might lead to nutritional losses. The results showed that eCO(2) under Fe-deficiency stimulates root dry weight from 0.37-0.80 g plant(-1) and shoot dry weight from 0.82-2.10 g plant(-1), without compromising root/shoot ratio. Besides, eCO(2) improved the chlorophyl content of Fe-deficient plants. However, downregulation of photosynthesis, reduction in stomatal conductance and transpiration rate, and an increase in water-use efficiency was observed due to eCO(2). Moreover, under Fe-deficiency, eCO(2) decreased K and Mg in roots, and Mg in leaves, whereas increased P and Zn in roots and leaves. In Fe-sufficient plants, eCO(2) increased K, P, Mn, Zn and Fe in leaves and did not change the concentration in roots. The Fe-deficiency-induced responses in roots, including the increase in FCR activity, and the expression of Fe-uptake genes were stimulated by eCO(2), but were not sufficient to increase Fe concentration in Fe-deficient plants.info:eu-repo/semantics/publishedVersio

Not so monochromatic: Size-dependency of both sex and color in the cleaner wrasse Labroides dimidiatus

In marine interspecific cleaning mutualisms, small fish known as “cleaners” inspect the surface, gills and sometimes the mouth of “client” reef fish, eating ectoparasites, mucus, scales and dead or infected tissue. These cleaner fish species share similar vivid coloration that makes them recognizable by clients. To gain insight on additional communication roles of cleaner fish color, we tested if differences in color among cleaner wrasse Labroides dimidiatus individuals captured from the wild are explained by sex, body size or parasite loads. We found that males were larger, heavier and tended to have more saturated blue tails than females. We also found blue color saturation to be positively correlated with size, and that this size-dependence explains the trend for the sexes to differ in color. Parasite loads did not predict individual differences in color, but fish in our sample were not heavily parasitized. Other color traits (including yellow color saturation and black color brightness) did not differ between the sexes and were associated with morphological differences. Size-dependence of blue color may thus suggest that it is a condition-dependent signal that could be used in various types of inter- and intraspecific social interactions

Le parasite isopode, Anilocra physodes, nouvelle source de nourriture pour le poisson lézard Synodus saurus (Synodontidae)

Copyright © 2015 Société Française d'Ichtyologie.During a wide project carried out on the behavior and reproduction of the Atlantic lizardfish Synodus saurus in the Azores (NE Atlantic), specimens of the ectoparasitic isopod Anilocra physodes were discovered in various stomachs contents of these piscivorous predatory fish. This intriguing result allowed us to conclude for the first time that fish species can ingest their own parasites, which becomes doubly beneficial, since it releases them from para- sites but it is also a new food source.RÉSUMÉ: Au cours de différents travaux menés sur le comportement et la reproduction du poisson lézard de l’Atlantique, Synodus saurus, aux Açores (Atlantique NE), des ectoparasites isopodes, Anilocra physodes, ont été découverts dans divers contenus stomacaux de ces prédateurs piscivores. Ce résultat intriguant nous a permis de conclure pour la première fois que des espèces de poissons peuvent ingérer leurs propres parasites, ce qui peut être doublement bénéfi- que pour eux, qui, tout en s’en libérant, disposent d’une nouvelle source de nourriture

Effect of the interaction between elevated carbon dioxide and iron limitation on proteomic profiling of soybean

Elevated atmospheric CO2 (eCO2) and iron (Fe) availability are important factors affecting plant growth that may impact the proteomic profile of crop plants. In this study, soybean plants treated under Fe-limited (0.5 mM) and Fe-sufficient (20 mM) conditions were grown at ambient (400 μmol mol−1) and eCO2 (800 μmol mol−1) in hydroponic solutions. Elevated CO2 increased biomass from 2.14 to 3.14 g plant−1 and from 1.18 to 2.91 g plant−1 under Fe-sufficient and Fe-limited conditions, respectively, but did not affect leaf photosynthesis. Sugar concentration increased from 10.92 to 26.17 μmol g FW−1 in roots of Fe-sufficient plants and from 8.75 to 19.89 μmol g FW−1 of Fe-limited plants after exposure to eCO2. In leaves, sugar concentration increased from 33.62 to 52.22 μmol g FW−1 and from 34.80 to 46.70 μmol g FW−1 in Fe-sufficient and Fe-limited conditions, respectively, under eCO2. However, Fe-limitation decreases photosynthesis and biomass. Pathway enrichment analysis showed that cell wall organization, glutathione metabolism, photosynthesis, stress-related proteins, and biosynthesis of secondary compounds changed in root tissues to cope with Fe-stress. Moreover, under eCO2, at sufficient or limited Fe supply, it was shown an increase in the abundance of proteins involved in glycolysis, starch and sucrose metabolism, biosynthesis of plant hormones gibberellins, and decreased levels of protein biosynthesis. Our results revealed that proteins and metabolic pathways related to Fe-limitation changed the effects of eCO2 and negatively impacted soybean production.info:eu-repo/semantics/publishedVersio